A137745 Number of different strings of length n obtained from "abcde" by iteratively duplicating any substring.
0, 0, 0, 0, 0, 1, 5, 19, 66, 218, 700, 2218, 6997, 22064, 69662, 220395, 699090, 2224114, 7098773, 22733498, 73048903, 235504760, 761689193, 2471105355, 8040439771, 26235143469, 85831045851, 281519068056, 925596771195, 3050264328190, 10074150332305, 33341934697311, 110571437129989
Offset: 0
Keywords
Examples
a(k) = 0 for k<5, since no shorter string can be obtained by duplicating a substring.
a(5) = # { abcde },
a(6) = # { aabcde, abbcde, abccde, abcdde, abcdee },
a(7) = # { aaabcde, aabbcde, aabccde, aabcdde, aabcdee, ababcde, abbbcde, abbccde, abbcdde, abbcdee, abcbcde, abcccde, abccdde, abccdee, abcdcde, abcddde, abcddee, abcdede, abcdeee }
Extensions
a(14)-a(19) from Lars Blomberg, Jan 12 2013
a(20)-a(21) from Michael S. Branicky, Jan 05 2021
a(22)-a(23) from Bert Dobbelaere, Jun 10 2024
a(24)-a(32) from Martin Fuller, Jun 07 2025
Comments